阅读说明：本技术 一种适用于磷酸镁水泥的复合缓凝剂 (Composite retarder suitable for magnesium phosphate cement ) 是由 焦宝祥 高宇航 孟长 邹翔 徐海笑 韩俊哲 于 2021-11-03 设计创作，主要内容包括：本发明公开了一种适用于磷酸镁水泥的复合缓凝剂,属于建筑材料技术领域。所述复合缓凝剂由如下重量份的组分组成：40～55份硼砂,40～50份苹果酸或苹果酸盐,5～10份尿素。该复合缓凝剂对磷酸镁水泥具有较好的缓凝效果,不仅大大延长磷酸镁水泥的凝结时间,而且所制备的磷酸镁水泥抗压强度比同掺量的硼砂高,使得水泥既能满足施工时间要求,又能满足强度要求,是一种可以兼顾凝结时间和强度的优质缓凝剂,并且不含氯盐。(The invention discloses a composite retarder suitable for magnesium phosphate cement, and belongs to the technical field of building materials. The composite retarder comprises the following components in parts by weight: 40-55 parts of borax, 40-50 parts of malic acid or malate and 5-10 parts of urea. The composite retarder has a good retarding effect on magnesium phosphate cement, the setting time of the magnesium phosphate cement is greatly prolonged, the compressive strength of the prepared magnesium phosphate cement is higher than that of borax with the same doping amount, so that the cement can meet the requirement of construction time and strength, is a high-quality retarder which can give consideration to the setting time and strength, and does not contain chloride.)

1. The composite retarder suitable for magnesium phosphate cement is characterized by comprising the following components in parts by weight: 40-55 parts of borax, 40-50 parts of malic acid or malate and 5-10 parts of urea.

2. The composite retarder suitable for magnesium phosphate cement as claimed in claim 1, wherein the malate is selected from one or a combination of more than two of sodium malate, potassium malate and ammonium malate in any proportion.

3. The magnesium phosphate cement material is characterized by comprising the following components in parts by weight: the specific surface area is 2200 and 2800cm²350-370 parts of magnesium oxide per gram, 110-130 parts of monopotassium phosphate, 30-40 parts of the composite retarder according to claim 1 or 2 and 50-60 parts of water.

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to a composite retarder suitable for magnesium phosphate cement.

Technical Field

Magnesium Phosphate Cement (MPC) is a new hydraulic cementing material which is quickly hardened by acid-alkali reaction and physical action after adding water, has the characteristics of short setting time and high early strength, can be applied to quickly repairing the local damaged or structural failure part of a building, has good compatibility and cohesiveness with the old concrete, and has better frost resistance and volume stability than portland cement. However, when the magnesium phosphate cement is applied, the setting time is too fast, the consistency is high, and the operability is poor during construction, so that the magnesium phosphate cement has certain limitation in use.

The addition of the retarder not only can increase the setting time of the magnesium phosphate cement repairing material, but also can reduce the hydration heat release in the hardening process. The commonly used retarder for magnesium phosphate cement at present comprises borax, boric acid, sodium tripolyphosphate and the like, wherein the borax is the most widely used retarder for the magnesium phosphate cement. When in application, the borax doping amount is generally 5 percent of the mass of the magnesium oxide, and the setting time is 5 min; when sodium tripolyphosphate is used as a retarder, the mixing amount of the sodium tripolyphosphate is usually 2-10% of the mass of magnesium oxide, and the setting time can only be prolonged to 10 min. Therefore, there is still a problem that the setting time is relatively short, and the strength of the magnesium phosphate cement is decreased as the amount of the admixture is increased.

The Chinese patent with application number 201010169618.2 discloses a method for controlling setting time and early hydration speed of magnesium potassium phosphate cement, which comprises the steps of compounding borax, disodium hydrogen phosphate dodecahydrate and chloride according to a proportion to obtain a compound retarder, and controlling the setting time within 10 minutes to 6 hours by adjusting the content of the disodium hydrogen phosphate dodecahydrate and the chloride; the setting time of magnesium phosphate cement (20-25 of university of Wuhan theory of Industrial science, 2014,36 (10)) is adjusted by adopting a multi-component composite retarder containing calcium chloride, and the setting time reaches 40 min. However, both of the two composite retarders contain chloride salt, which has a corrosive effect on steel, so that the use of the retarder has certain limitation. Therefore, there is still a need to develop a new chloride-free retarder to meet the market demand.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned disadvantages of the prior art, and an object of the present invention is to provide a composite retarder for magnesium phosphate cement, which can greatly prolong the setting time of magnesium phosphate cement, has an excellent retardation effect, does not contain chloride salt, and can improve the strength of magnesium phosphate cement.

Technical scheme

A composite retarder suitable for magnesium phosphate cement is composed of the following components in parts by weight: 40-55 parts of borax, 40-50 parts of malic acid or malate and 5-10 parts of urea.

Further, the malate is selected from one or a combination of more than two of sodium malate, potassium malate and ammonium malate in any proportion.

The magnesium phosphate cement material comprises the following components in parts by weight: the specific surface area is 2200 and 2800cm²350-370 parts of magnesium oxide per gram, 110-130 parts of monopotassium phosphate, 30-40 parts of the composite retarder according to claim 1 or 2 and 50-60 parts of water.

The invention has the beneficial effects that: the novel composite retarder overcomes the problems that the coagulation regulating effect of magnesium phosphate cement prepared by a single inorganic retarder is poor, and the strength is rapidly reduced along with the increase of the mixing amount. The novel composite retarder can effectively adjust the setting time of magnesium phosphate cement, and meanwhile, the strength is not seriously reduced along with the increase of the doping amount within the doping amount range, so that the quick-setting early-strength cement can prolong the construction time, can meet the strength requirement, and does not contain chloride salt which can rust steel bars.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples. The present invention can be better understood from the following examples and comparative examples. However, the specific material ratios, process conditions and results thereof described in the examples and comparative examples are only for illustrating the present invention and are only for helping those skilled in the art to understand the present invention, and should not be construed as limiting the present invention described in detail in the claims.

Comparative example 1

Borax is selected as a retarder.

Comparative example 2

Ammonium acetate and borax are selected as retarders, and the mass ratio of the ammonium acetate to the borax is 1: 1.

Comparative example 3

Citric acid and borax are selected as retarders, and the mass ratio of the citric acid to the borax is 1: 1.

Comparative example 4

Selecting citric acid, borax and urea as a retarder, wherein the mass ratio of the citric acid to the borax to the urea is 1: 0.9: 0.1.

example 1

A composite retarder suitable for magnesium phosphate cement is composed of the following components in parts by weight: 50 parts of borax, 45 parts of malic acid and 5 parts of urea.

Example 2

A composite retarder suitable for magnesium phosphate cement is composed of the following components in parts by weight: 50 parts of borax, 45 parts of sodium malate and 5 parts of urea.

Example 3

A composite retarder suitable for magnesium phosphate cement is composed of the following components in parts by weight: 50 parts of borax, 40 parts of malic acid and 10 parts of urea.

The retarder of comparative examples 1 to 4 and examples 1 to 3 was used to prepare magnesium phosphate cement materials by the following method: the specific surface area is 2320cm²And uniformly mixing 360 parts per gram of magnesium oxide, 36 parts of retarder and 57.6 parts of water, adding 120 parts of monopotassium phosphate, and uniformly stirring to obtain the magnesium phosphate cement material.

(1) The setting time of the magnesium phosphate cement material is measured at 20 ℃ by referring to GB/T1346-2011, and the result is shown in the following table 1:

TABLE 1 measurement results of setting time at 20 ℃ for magnesium phosphate cement materials

	Initial setting	Final setting
			Comparative example 1	8min	11min
Comparative example 2	9min	13min
			Comparative example 3	7min30s	11min
Comparative example 4	2min30s	5min
			Example 1	15min	31min
Example 2	15min	32min
			Example 3	23min	38min

As can be seen from the test results in Table 1, compared with the retarders of comparative examples 1-4, the setting time of the magnesium phosphate cement can be greatly prolonged by adopting the composite retarder of the embodiment of the invention under the same mixing amount, and the retarding effect is obvious.

(2) Pouring magnesium phosphate cement materials into a mold with the size of 20mm multiplied by 20mm, vibrating each group of 6 blocks on a laboratory vibration table for 1min, strickling, putting into a curing box with the temperature of 20 ℃ and the relative humidity of 90% for curing, removing the mold after 3h, putting into the curing box for curing to the age of 1d, 3d, 7d and 28d, and measuring the compressive strength of the samples, wherein the stirring mode of the MPC mortar strength samples is executed according to JC/T2537-2019 'magnesium phosphate repair mortar', and the compressive strength of the MPC mortar is executed according to GB/T17671-1999 'cement mortar strength test method (ISO method)'.

The test results are shown in table 2:

TABLE 2 compression Strength measurement results of magnesium phosphate Cement paste at 20 ℃ at 1d, 3d, 7d and 28d

As can be seen from the test results in Table 2, the compressive strength of the magnesium phosphate cement can be improved by using the composite retarder of the embodiment of the invention in the same amount as compared with the retarders of the comparative examples 1 to 4.